After the biggest crisis of his premiership David Cameron talks about how to
fix a broken society, and the contagion of despair in Britain's bleakest
neighbourhoods.

What kept you? That's the first thing I want to ask David Cameron, as I sit down opposite him on the mid-morning train from Euston to Manchester. On Monday night, I say, I took refuge with my children in a friend's house in Hackney, a few hundred yards further away from the boiling disorder, far enough to feel safe; and, as I watched the scenes of conflagration and looting unfold on-screen, I did ask out loud: where is our Prime Minister?

Politicians of Cameron's sangfroid rarely squirm - but the question makes him visibly uneasy. "Well, I was on my way back," he says. "I was at my desk on Tuesday morning and look, I don't think I could have hindsight is a wonderful thing, but I don't think I could have got back much faster.

"There wasn't a clamour on Sunday. I spent a lot of the time on the telephone on euro-zone issues, and the economy then everything turned and changed. But look - it was important as soon as what was happening on Monday was apparent, to get back quickly and that's what I did."

It was clear, he agrees, that "the captain of the ship had to be on the deck", and, since his return from his Tuscan holiday, he has been working round the clock – including a marathon 165 minute performance in the emergency Commons debate on Thursday. His wife calls just before we start talking and then once again during the interview. Cameron clearly longs to be back with his family ("I'll switch this off. No, I'll switch it to silent.") But he knows that, more than at any moment in 15 months of his premiership, he is needed on the bridge.

The nature of the emergency converges with his longstanding passion for the social issues it has raised: responsibility, the broken society, welfare dependency, social mobility, family breakdown, and the contagion of despair in Britain's bleakest neighbourhoods.

In the twenty odd years I have known him, I have never seen Cameron so animated, so consumed by a sense of urgency. We are en route to Salford where he will survey one of the scenes of last week's riots - a burnt-out Lidl store – and talk to firefighters, police officers and local residents .

Another cup of black coffee is drained. The remains of a banana nestles between his two phones. He repeatedly makes his point by punching his palm, or bringing his hand down hard on the table.

It is overwhelmingly clear that he sees this as a fork in the road rather than as a spot of midsummer madness that will fade quickly in the memory.

New measures, new strategies and new thinking will be required. I mention the "zero tolerance" approach to anti-social behaviour – an approach most famously taken by Mayor Giuliani in New York after 1993 – and ask if he sees potential in the idea. He leaps on the suggestion.

"Yes, I do. This is why I am so keen on police accountability, where you see police chiefs accountable to elected representatives, as you do in London, I don't think it is any surprise London was one of the first places to introduce that sort of beat-based policing with a far greater degree of zero tolerance."

Bill Bratton, the former Los Angeles police chief much admired by Cameron, was a pioneer of the "zero tolerance" approach while head of the New York City Transit Police in the 1990s.

At the heart of this philosophy of civil order is the idea that there is a spectrum of anti-social behaviour that begins with breaking windows and ends with violent theft – or worse. On this basis, zero tolerance of petty offences can send a powerful social signal about much more serious crimes.

"I will be saying more about that because I think it is true," says Cameron, "I think it is demonstrably true. One of the interesting things about this week is that councils - although they might not always say [so] - believe it's true.

"Look how quickly local councils got in there and swept up the glass and actually made sure things were mended and looked better. They all know from their own experience that if you leave the broken window, the shop gets looted again.

"If you leave the bus shelter with graffiti all over it, it gets trashed even further. We haven't talked the language of zero tolerance enough, but the message is getting through. And this is an open door we should push at."

So: watch this space.

Already, he has taken wide soundings, not least from Blairite veterans like the former Communities Secretary, Hazel Blears, who is to accompany him on his tour of Salford after the interview. Tomorrow, in a speech in Witney (his constituency since 2001), the PM will explore some of the conclusions he has drawn thus far, and attempt to restore a measure of optimism to the debate.

At the heart of it all, he thinks, is the question of young men and their role models.

"You can see in boys that they yearn - I see it in my son [Arthur, aged 5], he yearns for time with his Dad alone, he wants to go for walks.

"It is extraordinary, this sense that you should do things together, and talk about things, and explain things, and it is brilliant. But, God, it's testing - no one tells you how to do it.

"I think we all rely on our friends to tell us 'You need to do this differently', and we watch our friends and how they parent, and we listen a bit to our Mums and Dads. If you haven't got that network, where do you get it from?"

Meanwhile, Number Ten is keen to smooth over relations with the police, after prickly remarks by Sir Hugh Orde, president of the Association of Chief Police Officers, and Tim Godwin, the acting Met Commissioner - so Cameron phrases his critique carefully.

"I do think that the police tactics didn't work to start with. But to be fair to the police, this was a changing [situation] If you go all the way back to Saturday, what was happening first of all, it was the police holding back because of what happened to Mark Duggan [the 29-year-old Tottenham man whose death triggered the initial disorder] and it's quite understandable why they held back.

But then what was a protest about Duggan turned into something else - looting - and it was at that point it was necessary to change tactics and to change approach - and that's difficult to recognize." Intimately connected to this is the question of police cuts. On that subject, the Conservative Mayor of London was unequivocal last week. "If you ask me whether I think there is a case for cutting police budgets in the light of these events," declared Boris. "then my answer to that would be no." But the Prime Minister and Chancellor are no less adamant.

"I have looked at this, and looked at it again, and looked at it again," says Cameron, "and frankly what we're asking the police to do [is] to find on average 6 per cent cash cuts over the next four years. Now, there isn't an organization in the country that hasn't had to find those sorts of efficiencies. I sat down with my Chief Constable, who comes to my constituency surgery, who took me though her budget line by line by line, and she showed me where she was going to find the savings, how they are going to cooperate with other forces, how they are going to do better on procurement, how they are going to get people out from behind their desks, how they are going to cut paperwork, and how they are going to do that without reducing visible policing. I absolutely believe it can be done and it's no good just immediately saying: 'Well, it's been a difficult week, so let's tear up police budgets and let's give up on that part of dealing with the deficit.'" After a week of cacophonous commentary, I ask Cameron if it is possible to over-analyse straightforward matters of criminality - to submerge simple issues of personal morality in a glutinous soup of sociology and liberal handwringing.

"I think there is a danger sometimes of people seeking very, very complicated answers when there are quite simple [explanations] these people who were nicking televisions were not complaining about the reform of the Education Maintenance Allowance or tuition fees.

"They were nicking televisions because they wanted a television and they weren't prepared to save up and get it like normal people."

That said, Cameron wants to look beyond the criminality to the broader context.

"The complicated bit is why are there so many, why is there this sizeable minority of people who are prepared to do this?"

He explicitly rejects the idea that "there is a bunch of children who are born evil."

The problems of parenting are universal. "I find with my own children that boundaries are really tough," he says, "and it is tough in the modern world because there are so many temptations and things they want."

But what if nobody is there to set boundaries?

"You read stories in the papers and it just makes you want to weep when you hear some of the parents describing how they just can't control their children and, anyway, it's not really their job."

At the heart of the response, he says, must be the meticulous targeting of time, energy and resources.

"I don't know if I can put a number on it - it might be 100,000 deeply broken and troubled families I think this is a real project for this Parliament in saying right, we know who they are, we know where they are, we know how you can help to strengthen a family. So let's roll up our sleeves, not be embarrassed with worries about 'is this a nanny state?' but these families are costing hundreds of millions of pounds for the country, they are completely dysfunctional, they need help and we are going to get in there and actually try and turn this around."

Nor does he rule out driving this from Downing Street: "There may well be more we need to do so the centre is really applying its grip and drive to this particular issue."

What is striking is that politicians almost invariably seek to drain the drama from the challenges they face. Cameron, in contrast, is positively raising the stakes. What has happened, he says, was "truly shocking, it was awful, we haven't seen anything like it on our streets for years. It is going to change things, definitely."

This is, he declares categorically, "a huge event in the life of the nation." And now we shall find out if the man is equal to the hour.